Advances in plasma processing have provided for growth in the semiconductor industry. During substrate processing, conditions of the chamber may have to be closely manipulated to create a processing environment that produces semiconductor devices. In a precision linear motion processing system, manipulation may occur by altering the configuration of the processing chamber.
Consider the situation wherein, for example, a substrate is being processed in a processing chamber of a precision linear motion processing system. The substrate is positioned on top of a lower electrode electrostatic chuck). Depending upon the recipe, the lower electrode may be moved vertically, thereby adjusting the substrate in relation to the upper electrode, which is usually positioned above the lower electrode.
To facilitate the vertical adjustment of the lower electrode, a linear motion apparatus may be attached to the lower electrode. The linear motion apparatus may include a leadscrew. To enable the leadscrew to rotate, a motor may be attached to the leadscrew via a shaft. The motorized leadscrew arrangement may be attached to the external wall of the processing chamber via a pair of clamps, which may be fastened to the wall of the processing chamber via a pair of screws.
The linear motion apparatus may also include a nut arrangement. The nut arrangement may include a threaded nut, which may surround the leadscrew to create a concentric relationship between the leadscrew and the threaded nut. The nut arrangement may be attached to a support plate, which is fastened to the threaded nut via a nut bracket. Accordingly, as the leadscrew rotates, the nut arrangement is moved in a vertical direction, thereby causing the support plate to move in the same direction. Since the support plate is attached to the lower electrode, the lower electrode is adjusted by manipulating the linear motion apparatus. In other words, the motorized leadscrew causes the nut arrangement to move in a vertical direction, thereby translating into a vertical adjustment of the lower electrode.
To maximize the life of the linear motion apparatus, the concentricity between the leadscrew and the threaded nut may have to be maintained. However, maintaining concentricity may be a challenge, especially if the linear motion apparatus may have been improperly assembled. In an example, during assembly of the precision linear motion processing system, the leadscrew may have been positioned in a manner slightly out of concentricity. Even if the linear motion apparatus has been assembled properly, leadscrew runout may occur. As discussed herein, leadscrew runout refers to a leadscrew that is not straight due to a manufacture defect, or normal manufacturing tolerances. Regardless if the linear motion apparatus has been improperly assembled or the leadscrew may have runout, the rotation of the leadscrew may cause the threaded nut to apply load to one side of the leadscrew, thereby causing excessive friction and/or premature wearing of the leadscrew and/or the threaded nut.
To address the misalignment, one prior art solution includes employing, a set of clearance slots to accommodate the fasteners that may be utilized to mount either hardware (e.g. leadscrew or threaded nut). In an example, a clamp may mount the leadscrew to the wall of the processing chamber. The clamp may be fastened to the wall of the processing chamber via a pair of screws, which may be inserted into a pair of clearance slots located on the clamp. Each clearance slot may have an oblong configuration, thereby enabling an assembler to align the leadscrew in an X direction. However, by using clearance slot to perform alignment, the simple assembly process becomes as time-consuming and more complicated assembly procedure. As a result, a highly-skilled assembler is required to perform the more complicated assembly procedure. In addition, unwanted side loading grinding against the side of the leadscrew) may still occur since the clearance slots do not address leadscrew runout.
Another prior art solution includes employing a floating nut, which is a threaded nut with a clearance gap at its mounting holes. In an example, a linear motion apparatus may include a leadscrew surrounded by a threaded nut mounted with holes with clearance gap. In other words, a gap may exist between the mounting screws and the mounting holes of the threaded nut. Accordingly, with a gap, misalignment due to improper assembly and/or leadscrew runout may be accommodated, thereby reducing unwanted side loading. However, the floating nut arrangement may cause the threaded nut to shift in a clockwise and/or counterclockwise direction. As a result, the shifting of the threaded nut may cause loss of positional accuracy that may translate to inability to accurately manipulate the configuration of the processing chamber in order to etch a substrate.
As can be appreciated from the foregoing, premature wearing due to unwanted side loading may require that at least part of the linear motion apparatus, such as the leadscrew and the threaded nut, be replaced. While the worn parts are being replaced, the processing tool is essentially unavailable for processing substrate. Depending upon the time period required to replace the worn parts (which may include shutting down the processing tool, ordering, the required parts, disassembling the linear motion apparatus, reassembling the linear motion apparatus with the new parts, recalibrating the processing tool, and the like), the economic loss that a company may suffer due to premature wearing can become quite significant.